let tag=document.getElementsByTagName('input')[0];
tag.checkValidity();
tag.setCustomValidity(null);
console.log(tag.validity.customError);
tag.setCustomValidity(undefined);
console.log(tag.validity.customError);
tag.setCustomValidity('');
console.log(tag.validity.customError);

tag.setCustomValidity('hint');
console.log(tag.validity.valid,
			tag.validationMessage,
			tag.willValidate,
			tag.validity.valueMissing,
			tag.validity.rangeOverflow,
			tag.validity.rangeUnderflow,
			tag.validity.patternMismatch,
			tag.validity.stepMismatch,
			tag.validity.typeMismatch,
			tag.validity.tooLong,
			tag.validity.tooShort
);
